When driving a load using a transistor component it is generally known to connect the transistor component in series with the load between terminals for first and second supply potentials or positive and negative supply potentials. Such a circuit arrangement is illustrated in FIG. 1. In this case, the reference symbol M designates a transistor component formed as a MOSFET, the load path of which is connected between a first connecting terminal K1 for a first supply potential +V and an output terminal OUT. A load L is connected between said output terminal OUT and a second connecting terminal K2 for a second supply potential GND, so that the load path of the transistor component M and the load L are connected in series between the connecting terminals K1, K2 for the supply potentials. The load path of the MOSFET M is formed by the drain-source path thereof. The MOSFET M can be driven via its gate terminal, which forms a control terminal, by a drive circuit 10 according to a switching signal Sin. The drive circuit 10 is designed to generate a drive signal Sdrv according to the switching signal Sin, which drive signal drives the MOSFET M in the on state or in the off state according to the switching signal Sin.
An example of such a circuit arrangement having a transistor component for driving a load and a drive circuit for driving the transistor component is the integrated device BTS 307 from Infineon Technologies AG, Munich, which belongs to the PROFET® family and is described in the data sheet PROFET® BTS 307, Oct. 1, 2003, Infineon Technologies AG, Munich. In this arrangement, a transistor component formed as a power MOSFET and the associated drive circuit are monolithically integrated in a semiconductor body/semiconductor chip.
If the transistor component M in the circuit in accordance with FIG. 1 is driven in the on state, then the voltage drop across its load path D-S is usually very small in comparison with the supply voltage present between the connecting terminals K1, K2. The supply voltage is thus present approximately exclusively across the load L. When driving an inductive load, a considerable voltage loading on the semiconductor switching element M may occur after the semiconductor switching element M has been turned off, which voltage loading may be significantly greater than the supply voltage, as is explained below with reference to FIG. 2.
It shall be assumed that the semiconductor switching element M is driven in the on state depending on the switching signal Sin up to an instant toff. The output voltage Vout present across the load L then essentially corresponds to the supply voltage +V. If the semiconductor switching element M is turned off at the switch-off instant toff, then upon commutation of the inductive load L a voltage is induced which causes the potential at the output terminal OUT to fall far below the reference potential GND present at the second connecting terminal K2, so that the voltage present across the semiconductor switching element M is significantly higher than the supply voltage +V.
This fall in the potential at the output terminal OUT when the transistor component M is turned off can be counteracted by connecting a diode D in parallel with the load L. This diode D has the effect that, upon commutation of the load L, the potential at the output terminal OUT falls below the value of the reference potential GND at most by the value of the forward voltage of the diode. The diode D acts as a freewheeling element and accepts the freewheeling current flowing upon commutation of the inductive load L.
What is disadvantageous about the previously explained solution is the need to have to use an additional external component in the form of the diode D, which increases the production costs and the complexity in the realization of the circuit.
Therefore, it would be advantageous to provide a circuit arrangement for driving a load, in particular for driving an inductive load, which has a freewheeling element and which can be realized simply and cost-effectively.